@Test
public void testSpin() throws OrekitException {
AbsoluteDate date =
new AbsoluteDate(
new DateComponents(1970, 01, 01),
new TimeComponents(3, 25, 45.6789),
TimeScalesFactory.getUTC());
KeplerianOrbit orbit =
new KeplerianOrbit(
7178000.0,
1.e-4,
FastMath.toRadians(50.),
FastMath.toRadians(10.),
FastMath.toRadians(20.),
FastMath.toRadians(30.),
PositionAngle.MEAN,
FramesFactory.getEME2000(),
date,
3.986004415e14);
final AttitudeProvider law =
new LofOffsetPointing(
earthSpheric,
new LofOffset(orbit.getFrame(), LOFType.VVLH, RotationOrder.XYX, 0.1, 0.2, 0.3),
Vector3D.PLUS_K);
Propagator propagator = new KeplerianPropagator(orbit, law);
double h = 0.01;
SpacecraftState sMinus = propagator.propagate(date.shiftedBy(-h));
SpacecraftState s0 = propagator.propagate(date);
SpacecraftState sPlus = propagator.propagate(date.shiftedBy(h));
// check spin is consistent with attitude evolution
double errorAngleMinus =
Rotation.distance(
sMinus.shiftedBy(h).getAttitude().getRotation(), s0.getAttitude().getRotation());
double evolutionAngleMinus =
Rotation.distance(sMinus.getAttitude().getRotation(), s0.getAttitude().getRotation());
Assert.assertEquals(0.0, errorAngleMinus, 1.0e-6 * evolutionAngleMinus);
double errorAnglePlus =
Rotation.distance(
s0.getAttitude().getRotation(), sPlus.shiftedBy(-h).getAttitude().getRotation());
double evolutionAnglePlus =
Rotation.distance(s0.getAttitude().getRotation(), sPlus.getAttitude().getRotation());
Assert.assertEquals(0.0, errorAnglePlus, 1.0e-6 * evolutionAnglePlus);
Vector3D spin0 = s0.getAttitude().getSpin();
Vector3D reference =
AngularCoordinates.estimateRate(
sMinus.getAttitude().getRotation(), sPlus.getAttitude().getRotation(), 2 * h);
Assert.assertTrue(spin0.getNorm() > 1.0e-3);
Assert.assertEquals(0.0, spin0.subtract(reference).getNorm(), 1.0e-10);
}
@Test
public void testResetState() throws OrekitException {
final List<AbsoluteDate> reset = new ArrayList<AbsoluteDate>();
DateDetector raw =
new DateDetector(orbit.getDate().shiftedBy(3600.0))
.withMaxCheck(1000.0)
.withHandler(
new EventHandler<DateDetector>() {
public SpacecraftState resetState(
DateDetector detector, SpacecraftState oldState) {
reset.add(oldState.getDate());
return oldState;
}
public Action eventOccurred(
SpacecraftState s, DateDetector detector, boolean increasing) {
return Action.RESET_STATE;
}
});
for (int i = 2; i < 10; ++i) {
raw.addEventDate(orbit.getDate().shiftedBy(i * 3600.0));
}
EventEnablingPredicateFilter<DateDetector> filtered =
new EventEnablingPredicateFilter<DateDetector>(
raw,
new EnablingPredicate<DateDetector>() {
public boolean eventIsEnabled(
SpacecraftState state, DateDetector eventDetector, double g) {
return state.getDate().durationFrom(orbit.getDate()) > 20000.0;
}
});
Propagator propagator = new KeplerianPropagator(orbit);
EventsLogger logger = new EventsLogger();
propagator.addEventDetector(logger.monitorDetector(filtered));
propagator.propagate(orbit.getDate().shiftedBy(Constants.JULIAN_DAY));
List<LoggedEvent> events = logger.getLoggedEvents();
Assert.assertEquals(4, events.size());
Assert.assertEquals(
6 * 3600, events.get(0).getState().getDate().durationFrom(orbit.getDate()), 1.0e-6);
Assert.assertEquals(
7 * 3600, events.get(1).getState().getDate().durationFrom(orbit.getDate()), 1.0e-6);
Assert.assertEquals(
8 * 3600, events.get(2).getState().getDate().durationFrom(orbit.getDate()), 1.0e-6);
Assert.assertEquals(
9 * 3600, events.get(3).getState().getDate().durationFrom(orbit.getDate()), 1.0e-6);
Assert.assertEquals(4, reset.size());
Assert.assertEquals(6 * 3600, reset.get(0).durationFrom(orbit.getDate()), 1.0e-6);
Assert.assertEquals(7 * 3600, reset.get(1).durationFrom(orbit.getDate()), 1.0e-6);
Assert.assertEquals(8 * 3600, reset.get(2).durationFrom(orbit.getDate()), 1.0e-6);
Assert.assertEquals(9 * 3600, reset.get(3).durationFrom(orbit.getDate()), 1.0e-6);
}
@Test
public void testFrance() throws OrekitException {
final BodyShape earth =
new OneAxisEllipsoid(
Constants.WGS84_EARTH_EQUATORIAL_RADIUS,
Constants.WGS84_EARTH_FLATTENING,
FramesFactory.getITRF(IERSConventions.IERS_2010, true));
GeographicZoneDetector d =
new GeographicZoneDetector(20.0, 1.e-3, earth, buildFrance(), FastMath.toRadians(0.5))
.withHandler(new ContinueOnEvent<GeographicZoneDetector>());
Assert.assertEquals(20.0, d.getMaxCheckInterval(), 1.0e-15);
Assert.assertEquals(1.0e-3, d.getThreshold(), 1.0e-15);
Assert.assertEquals(0.5, FastMath.toDegrees(d.getMargin()), 1.0e-15);
Assert.assertEquals(AbstractDetector.DEFAULT_MAX_ITER, d.getMaxIterationCount());
final TimeScale utc = TimeScalesFactory.getUTC();
final Vector3D position = new Vector3D(-6142438.668, 3492467.56, -25767.257);
final Vector3D velocity = new Vector3D(505.848, 942.781, 7435.922);
final AbsoluteDate date = new AbsoluteDate(2003, 9, 16, utc);
final Orbit orbit =
new EquinoctialOrbit(
new PVCoordinates(position, velocity),
FramesFactory.getEME2000(),
date,
Constants.EIGEN5C_EARTH_MU);
Propagator propagator =
new EcksteinHechlerPropagator(
orbit,
Constants.EIGEN5C_EARTH_EQUATORIAL_RADIUS,
Constants.EIGEN5C_EARTH_MU,
Constants.EIGEN5C_EARTH_C20,
Constants.EIGEN5C_EARTH_C30,
Constants.EIGEN5C_EARTH_C40,
Constants.EIGEN5C_EARTH_C50,
Constants.EIGEN5C_EARTH_C60);
EventsLogger logger = new EventsLogger();
propagator.addEventDetector(logger.monitorDetector(d));
propagator.propagate(date.shiftedBy(10 * Constants.JULIAN_DAY));
Assert.assertEquals(26, logger.getLoggedEvents().size());
}
@Test
public void testEphemerisDatesBackward() throws OrekitException {
// setup
TimeScale tai = TimeScalesFactory.getTAI();
AbsoluteDate initialDate = new AbsoluteDate("2015-07-05", tai);
AbsoluteDate startDate = new AbsoluteDate("2015-07-03", tai).shiftedBy(-0.1);
AbsoluteDate endDate = new AbsoluteDate("2015-07-04", tai);
Frame eci = FramesFactory.getGCRF();
KeplerianOrbit orbit =
new KeplerianOrbit(
600e3 + Constants.WGS84_EARTH_EQUATORIAL_RADIUS,
0,
0,
0,
0,
0,
PositionAngle.TRUE,
eci,
initialDate,
mu);
double[][] tol = NumericalPropagator.tolerances(1, orbit, OrbitType.CARTESIAN);
Propagator prop =
new NumericalPropagator(new DormandPrince853Integrator(0.1, 500, tol[0], tol[1]));
prop.resetInitialState(new SpacecraftState(new CartesianOrbit(orbit)));
// action
prop.setEphemerisMode();
prop.propagate(endDate, startDate);
BoundedPropagator ephemeris = prop.getGeneratedEphemeris();
// verify
TimeStampedPVCoordinates actualPV = ephemeris.getPVCoordinates(startDate, eci);
TimeStampedPVCoordinates expectedPV = orbit.getPVCoordinates(startDate, eci);
MatcherAssert.assertThat(
actualPV.getPosition(), OrekitMatchers.vectorCloseTo(expectedPV.getPosition(), 1.0));
MatcherAssert.assertThat(
actualPV.getVelocity(), OrekitMatchers.vectorCloseTo(expectedPV.getVelocity(), 1.0));
MatcherAssert.assertThat(
ephemeris.getMinDate().durationFrom(startDate), OrekitMatchers.closeTo(0, 0));
MatcherAssert.assertThat(
ephemeris.getMaxDate().durationFrom(endDate), OrekitMatchers.closeTo(0, 0));
// test date
AbsoluteDate date = endDate.shiftedBy(-0.11);
Assert.assertEquals(ephemeris.propagate(date).getDate().durationFrom(date), 0, 0);
}
@Test
public void testExceedHistoryBackward() throws OrekitException, IOException {
final double period = 900.0;
// the raw detector should trigger one event at each 900s period
final DateDetector raw =
new DateDetector(orbit.getDate().shiftedBy(+0.5 * period))
.withMaxCheck(period / 3)
.withHandler(new ContinueOnEvent<DateDetector>());
for (int i = 0; i < 300; ++i) {
raw.addEventDate(orbit.getDate().shiftedBy(-(i + 0.5) * period));
}
// in fact, we will filter out half of these events, so we get only one event every 2 periods
final EventEnablingPredicateFilter<DateDetector> filtered =
new EventEnablingPredicateFilter<DateDetector>(
raw,
new EnablingPredicate<DateDetector>() {
public boolean eventIsEnabled(
SpacecraftState state, DateDetector eventDetector, double g) {
double nbPeriod = orbit.getDate().durationFrom(state.getDate()) / period;
return ((int) FastMath.floor(nbPeriod)) % 2 == 1;
}
});
Propagator propagator = new KeplerianPropagator(orbit);
EventsLogger logger = new EventsLogger();
propagator.addEventDetector(logger.monitorDetector(filtered));
propagator.propagate(orbit.getDate().shiftedBy(-301 * period));
List<LoggedEvent> events = logger.getLoggedEvents();
// 300 periods, 150 events as half of them are filtered out
Assert.assertEquals(150, events.size());
// as we have encountered a lot of enabling status changes, we exceeded the internal history
// if we try to display again the filtered g function for dates far in the future,
// we will not see the zero crossings anymore, they have been lost
propagator.clearEventsDetectors();
for (double dt = -5000.0; dt > -10000.0; dt -= 3.0) {
double filteredG = filtered.g(propagator.propagate(orbit.getDate().shiftedBy(dt)));
Assert.assertTrue(filteredG < 0.0);
}
// on the other hand, if we try to display again the filtered g function for future dates
// that are still inside the history, we still see the zero crossings
for (double dt = -195400.0; dt > -196200.0; dt -= 3.0) {
double filteredG = filtered.g(propagator.propagate(orbit.getDate().shiftedBy(dt)));
if (dt < -195750) {
Assert.assertTrue(filteredG < 0.0);
} else {
Assert.assertTrue(filteredG > 0.0);
}
}
}
private void doElevationTest(
final double minElevation,
final AbsoluteDate start,
final AbsoluteDate end,
final int expectedEvents,
final boolean sameSign)
throws OrekitException {
final ElevationExtremumDetector raw =
new ElevationExtremumDetector(0.001, 1.e-6, new TopocentricFrame(earth, gp, "test"))
.withHandler(new ContinueOnEvent<ElevationExtremumDetector>());
final EventEnablingPredicateFilter<ElevationExtremumDetector> aboveGroundElevationDetector =
new EventEnablingPredicateFilter<ElevationExtremumDetector>(
raw,
new EnablingPredicate<ElevationExtremumDetector>() {
public boolean eventIsEnabled(
final SpacecraftState state,
final ElevationExtremumDetector eventDetector,
final double g)
throws OrekitException {
return eventDetector.getElevation(state) > minElevation;
}
})
.withMaxCheck(60.0);
Assert.assertEquals(0.001, raw.getMaxCheckInterval(), 1.0e-15);
Assert.assertEquals(60.0, aboveGroundElevationDetector.getMaxCheckInterval(), 1.0e-15);
Assert.assertEquals(1.0e-6, aboveGroundElevationDetector.getThreshold(), 1.0e-15);
Assert.assertEquals(
AbstractDetector.DEFAULT_MAX_ITER, aboveGroundElevationDetector.getMaxIterationCount());
Propagator propagator =
new EcksteinHechlerPropagator(
orbit,
Constants.EIGEN5C_EARTH_EQUATORIAL_RADIUS,
Constants.EIGEN5C_EARTH_MU,
Constants.EIGEN5C_EARTH_C20,
Constants.EIGEN5C_EARTH_C30,
Constants.EIGEN5C_EARTH_C40,
Constants.EIGEN5C_EARTH_C50,
Constants.EIGEN5C_EARTH_C60);
EventsLogger logger = new EventsLogger();
propagator.addEventDetector(logger.monitorDetector(aboveGroundElevationDetector));
propagator.propagate(start, end);
for (LoggedEvent e : logger.getLoggedEvents()) {
final double eMinus = raw.getElevation(e.getState().shiftedBy(-10.0));
final double e0 = raw.getElevation(e.getState());
final double ePlus = raw.getElevation(e.getState().shiftedBy(+10.0));
Assert.assertTrue(e0 > eMinus);
Assert.assertTrue(e0 > ePlus);
Assert.assertTrue(e0 > minElevation);
}
Assert.assertEquals(expectedEvents, logger.getLoggedEvents().size());
propagator.clearEventsDetectors();
double g1Raw = raw.g(propagator.propagate(orbit.getDate().shiftedBy(18540.0)));
double g2Raw = raw.g(propagator.propagate(orbit.getDate().shiftedBy(18624.0)));
double g1 =
aboveGroundElevationDetector.g(propagator.propagate(orbit.getDate().shiftedBy(18540.0)));
double g2 =
aboveGroundElevationDetector.g(propagator.propagate(orbit.getDate().shiftedBy(18624.0)));
Assert.assertTrue(g1Raw > 0);
Assert.assertTrue(g2Raw < 0);
if (sameSign) {
Assert.assertTrue(g1 > 0);
Assert.assertTrue(g2 < 0);
} else {
Assert.assertTrue(g1 < 0);
Assert.assertTrue(g2 > 0);
}
}
protected void checkFit(
final TLE tle,
final double duration,
final double stepSize,
final double threshold,
final boolean positionOnly,
final boolean withBStar,
final double expectedRMS)
throws OrekitException {
Propagator p = TLEPropagator.selectExtrapolator(tle);
List<SpacecraftState> sample = new ArrayList<SpacecraftState>();
for (double dt = 0; dt < duration; dt += stepSize) {
sample.add(p.propagate(tle.getDate().shiftedBy(dt)));
}
TLEPropagatorBuilder builder =
new TLEPropagatorBuilder(
tle.getSatelliteNumber(),
tle.getClassification(),
tle.getLaunchYear(),
tle.getLaunchNumber(),
tle.getLaunchPiece(),
tle.getElementNumber(),
tle.getRevolutionNumberAtEpoch());
FiniteDifferencePropagatorConverter fitter =
new FiniteDifferencePropagatorConverter(builder, threshold, 1000);
if (withBStar) {
fitter.convert(sample, positionOnly, TLEPropagatorBuilder.B_STAR);
} else {
fitter.convert(sample, positionOnly);
}
TLEPropagator prop = (TLEPropagator) fitter.getAdaptedPropagator();
TLE fitted = prop.getTLE();
Assert.assertEquals(expectedRMS, fitter.getRMS(), 0.001 * expectedRMS);
Assert.assertEquals(tle.getSatelliteNumber(), fitted.getSatelliteNumber());
Assert.assertEquals(tle.getClassification(), fitted.getClassification());
Assert.assertEquals(tle.getLaunchYear(), fitted.getLaunchYear());
Assert.assertEquals(tle.getLaunchNumber(), fitted.getLaunchNumber());
Assert.assertEquals(tle.getLaunchPiece(), fitted.getLaunchPiece());
Assert.assertEquals(tle.getElementNumber(), fitted.getElementNumber());
Assert.assertEquals(tle.getRevolutionNumberAtEpoch(), fitted.getRevolutionNumberAtEpoch());
final double eps = 1.0e-5;
Assert.assertEquals(tle.getMeanMotion(), fitted.getMeanMotion(), eps * tle.getMeanMotion());
Assert.assertEquals(tle.getE(), fitted.getE(), eps * tle.getE());
Assert.assertEquals(tle.getI(), fitted.getI(), eps * tle.getI());
Assert.assertEquals(
tle.getPerigeeArgument(), fitted.getPerigeeArgument(), eps * tle.getPerigeeArgument());
Assert.assertEquals(tle.getRaan(), fitted.getRaan(), eps * tle.getRaan());
Assert.assertEquals(tle.getMeanAnomaly(), fitted.getMeanAnomaly(), eps * tle.getMeanAnomaly());
if (withBStar) {
Assert.assertEquals(tle.getBStar(), fitted.getBStar(), eps * tle.getBStar());
}
}
